Anaerobic digestion is a method used for converting industrial or municipal organic byproducts or substrates into clean and renewable energy in which microorganisms are used to break down biodegradable materials in the absence of oxygen. It is commonly used to treat wastewater and organic waste. Anaerobic digestion produces gases (e.g., methane) and nutrient-rich solids which can be recovered and used. Accordingly, the byproducts of anaerobic digestion are a renewable energy source that can be used, for example, in place of fossil fuels. In addition, the nutrient-rich solids that are a byproduct of the digestion process can be used for soil amendment (e.g., fertilizer).
Commercial anaerobic digesters used at breweries typically do not digest spent grain or high strength wastewater. Digesters used at breweries are limited in application to waste that is substantially liquid with chemical oxygen demand (“COD”) levels of about 5,000 ppm. Spent grain and high strength wastewater are typically hauled offsite and used as a feed supplement for hogs and cattle. This limits the renewable energy production to about 5% of the potential renewable energy production that would be achieved if the high strength wastewater and spent grain were also efficiently anaerobically digested.
A need therefore exists for improved systems and methods for processing organic waste, and in particular, brewery waste.